What are queue lengths?

Queue lengths are how many people or things are waiting in line for something.

Imagine you're at a toy store on Saturday morning. There's only one cashier, and everyone wants to buy their favorite toy. So instead of just walking straight up to the counter, people have to stand behind each other, that’s a queue. The number of people standing there is the queue length.

Think about a slide at the park. If only one kid can go down at a time, and ten kids want to play, they’ll all line up. That long line is the queue length, it shows how many kids are waiting for their turn. The longer the line, the bigger the queue length.

If more kids come to join the line, the queue length grows. If some kids leave before their turn, it gets shorter. It’s just like when you're waiting in line at the store, if someone goes away, there's less people behind you!